The present invention relates to an optical cable in accordance with the preamble of Patent claim 1.
The construction in airports and other service centres of a modern data and communications network satisfying high safety standards necessitates the use and laying of large quantities of cables whose function and mechanical strength are largely maintained in the case of a fire. Moreover, it must be ensured that the flames cannot spread through cable ducts into other parts of buildings, that the combustion gases possibly released are non-toxic, and that the density of the ensuing smoke satisfies the so-called low-smoke conditions.
Data and communication cables having appropriate properties are disclosed, for example, in EP 0 708 455 A1, GB 2 138 168 B or DE 195 17 392 A1. Because of their complex structure, the production of these cables is, however, comparatively complicated and associated with high costs. Moreover, during a fire combustible gases are produced which escape from the cable core and can contribute to spreading of the flames.
The aim of the invention is to create an optical cable which continues to function in the case of fire. At the same time, the spreading of the flames is to be prevented or at least distinctly delayed. This object is achieved by means of a cable having the features of Patent Claim 1. Expedient refinements and developments of the optical cable are the subject matter of the dependent claims.
The proposed optical cable essentially comprises a core containing a plurality of optical conductors (LWL), a non-combustible support element surrounding the core in the shape of a tube or cylinder, a fireproofing layer arranged on the support element and a sheath containing a thermal insulation layer. A material which solidifies under the action of heat and covers at least one side of the support element serves as fireproofing layer.
In a further variant, it is also possible to provide two support elements enclosing the fireproofing layer. Metal sheets, foils, tapes, meshes, grids or structures in the form of gratings came particularly into consideration as support elements.
The support element is preferably corrugated or folded so that in the case of a fire it is formed or deformed very easily and without being damaged and does not allow the possibly combustible gases produced in the cable core to escape to the outside.